Project 3. Interactions in the Corticostriatal Network: Disruption of basal ganglia function leads to severe motor and cognitive deficits in various clinical conditions. Although the exact nature of basal ganglia functions remains elusive, recent progress in the study of basal ganglia anatomy and physiology have generated specific computational theories that can be tested in behaving animals. Because the main inputs and outputs of the basal ganglia arise from multiple cortical areas, the basal ganglia are likely to play a major role in the control of cortical information processing. This project will focus on the interactions between the prefrontal cortex and the striatum by simultaneously recording single-unit and field-potential activity from multiple sites in these two structures. The proposed experiments will use monkeys trained to perform reward-based learning and decision-making tasks. The first experiment will test the hypothesis that the convergence of cortical inputs and reward signals conveyed by the dopamine neurons provides a substrate in the striatum to generate signals necessary to bias the process of response selection. The second experiment will determine whether the role of the basal ganglia is limited to a situation in which a stable pattern of response bias can be established, or whether the neurons in the striatum are also involved in a dynamic decision-making task where the animal is required to avoid a habitual pattern of responses. Finally, the neural recordings obtained in these two experiments will be analyzed extensively using a wide range of analytical techniques to determine whether the temporal structure in the activity of striatal neurons is systematically influenced by synchronized oscillations in the cortical inputs. Overall, the results from these experiments will advance our understanding of the nature of communications between the cortex and the basal ganglia. Project 3 will complement other projects examining the role of the basal ganglia, motor cortex, supplementary motor area (Project 4) and ventral premotor cortex (Project 5) in selecting responses from among discrete alternatives, contributing to our shared goal of understanding how interactions among motor structures contribute to the selection and execution of coordinated eye, head and hand movements.